For the demands of speeding-up, miniaturization, and the like in the recent years, a toner that is capable of being fixed at an even lower temperature is in demand. In order to meet such a demand, a toner in which a resin binder containing a crystalline resin and an amorphous resin is used is proposed. While a toner in which a crystalline resin and an amorphous resin are used as described above has improved low-temperature fixing ability, the toner described above is likely to have a lowered toner strength. As a result, since a toner is applied with a larger mechanical or thermal stress to meet the demands of the speeding-up and miniaturization, a disadvantage concerning the lowering of durability such as storage stability is generated.
In view of the above disadvantages, it is disclosed that a toner containing a polyester resin containing a composite of a crystalline polyester obtained by polycondensing an alcohol component containing an aliphatic diol having 2 to 6 carbon atoms in an amount of 80% by mol or more, and an aliphatic dicarboxylic acid component having 2 to 8 carbon atoms in an amount of 80% by mol or more; and
an amorphous polyester obtained by polycondensing an aliphatic diol having 2 to 6 carbon atoms in an amount of 20% by mol or more and a carboxylic acid component has excellent low-temperature fixing ability and storage stability, and also has excellent color reproducibility (see JP-A-2003-246920).
In addition, it is disclosed that a toner containing a resin binder containing a block copolymer or a graft copolymer obtained by chemically bonding 3 to 50 parts by weight of a crystalline polyester and 97 to 50 parts by weight of an ionically cross-linked amorphous vinyl polymer, wherein a chloroform-insoluble content is from 3 to 10% by weight of the copolymer has excellent offset resistance and low-temperature fixing ability (see JP-A-Hei-4-81770).
Further, a method for producing a toner including the steps of melt-kneading a crystalline polyester and an amorphous resin, and heat-treating a melt-kneaded mixture to obtain a toner which satisfies all of low-temperature fixing ability, storage property, and durability is proposed (see JPA-2005-308995 (US-A-2007/207401) and JP-A-2009-116175 (US-A-2009/116175)).